This application claims priority from Great Britain Application No. GB 0014713.2 filed Jun. 16, 2000.
The present invention relates to respirator systems of the type that provide a forced flow of air to the respirator wearer from a source of compressed air.
One common purpose of a respirator is to prevent contaminants from entering the respiratory system of the wearer. A respirator typically comprises a head piece in some form, shaped to provide a breathing zone around at least the nose and mouth of the wearer. In some respirators, the breathing action of the wearer alone causes air to be drawn into the breathing zone through a filter. Other respirators, however, provide a forced flow of filtered air to the breathing zone, thereby relieving the wearer of the need to inhale against the resistance of the filter and, at the same time, ensuring that any leakage in the respirator is outwards (that is, away from the breathing zone rather than into it). Respirators that use forced air flow are preferred in certain working environments, particularly those that are physically demanding on the wearer and those where the wearer is likely to benefit from the cooling effect of air flowing through the breathing zone.
A forced flow of air into the breathing zone of a respirator head piece may be generated by a fan or by a blower which, together with its power source, may be carried by the respirator wearer (known as a powered system). Alternatively, the forced flow of air may be obtained from a source of compressed air, which may be either fixed or portable (known as a supplied air system). In that case, the respirator head piece is connected to the air source through a regulator, to reduce the pressure at which air is supplied to the head piece to a suitable level. Examples of respirator head pieces suitable for use in supplied air systems are described in EP-A-0 602 847; GB-A-2 032 284, and in U.S. Pat. Nos. 3,963,021 and 4,280,491. In some supplied air systems, the pressure regulator is part of the equipment that is carried by the respirator wearer, in which case it is typically mounted on a belt at the wearer""s waist and is provided with a control knob, accessible to the wearer, by which the flow of air into the head piece can be adjusted. In other systems, in which the compressed air is provided through a wall-mounted socket, the pressure regulator may be located at the socket.
A so-called xe2x80x9cself-contained breathing apparatusxe2x80x9d, intended for use in a toxic environment or under water, also supplies the user with air obtained from a source of compressed air via one or more pressure regulators. In that case, however, the head piece is in the form of a tightly-fitting mask as described, for example, in WO 97/30753 and 97/46281, and in EP-A-0 631 795, 0 766 979 and 0 921 066. Generally, the compressed air pressures used in this type of system are comparatively high and the pressure regulator arrangements that are used are consequently more complex than those used in supplied air systems, for which standard (lower cost) regulator devices have typically been employed despite the fact that they offer the user much less control over the air flow into the head piece.
Sources of compressed air generate noise and, in the case of respirator systems and breathing apparatus, that noise can be transmitted to the head piece or mask and thus to the ears of the user. Despite the fact that exposure to such noise can be extremely unpleasant, noise reduction in respirator systems does not receive much attention and is often ignored completely. Examples of respirator systems that do incorporate noise reduction arrangements are those available, under the trade designations xe2x80x9cAirstream AH 18xe2x80x9d and xe2x80x9cVisionairxe2x80x9d, from Minnesota Mining and Manufacturing Company of St. Paul, Minn., USA. In the first-mentioned system, noise reduction is provided by two sintered discs contained in the low-pressure hose leading from the pressure regulator to the respirator head piece and, in the second system, it is provided by muffling the air supply tube within the head piece itself.
The cost of a respirator system is a particularly important factor because, even if a system offers particular advantages, users may be tempted for costs reasons to make do with an inferior system. Thus, although effective pressure regulation and noise reduction are known to be beneficial to the wearer and would make the use of a supplied air respirator system less unpleasant, they are often not provided for reasons of cost. The present invention is concerned with enabling pressure regulation and noise reduction to be provided in a respirator system at an acceptable cost.
The present invention provides a regulator assembly for use in a respirator system to supply a regulated flow of air to a respirator head piece; the assembly comprising:
a housing that comprises an air inlet port for connection to a source of air at comparatively high pressure, and an air outlet port for connection to the respirator head piece; the housing containing an air pressure-reduction stage in communication with the inlet port, and a noise-reduction stage located in the air flow path within the housing between the pressure-reduction stage and the outlet port; wherein the noise-reduction stage comprises first and second noise-reduction members spaced apart from each other along the air flow path, the first noise-reduction member being positioned adjacent the air outlet of the pressure-reduction stage, and including a deflector member arranged to deflect the air flow from the pressure-reduction stage through the first noise-reduction member and thereby diffuse the air flow before it reaches the second noise-reduction member.
As used herein, the term xe2x80x9cairxe2x80x9d includes breathable gases.
Through an appropriate configuration of the pressure-reduction stage that forms part of an assembly in accordance with the invention, a standard assembly that is suitable for use in many different supplied air respirator systems can be readily provided. This standardization offers the possibility of substantial cost reduction, making it possible in turn to provide effective pressure regulation and noise reduction in supplied air respirator systems at a reasonable price.